Clarkson was a leading campaigner against the slave trade and slavery in Britain and the British empire.
Thomas Clarkson was born on 28 March 1760 in Wisbech, Cambridgeshire. He was the son of a clergyman who also taught at the local grammar school. In 1779, Clarkson went to Cambridge University where he won a Latin essay competition on the subject of whether it was lawful to make slaves of others against their will.
While travelling from Cambridge to London in June 1785, Clarkson found himself thinking not about the competition, nor about the promising church career awaiting him, but about slavery. He got off his horse and sat down by the roadside at Wadesmill in Hertfordshire, feeling that someone should do something about this evil. Ending slavery became his driving passion for the remaining 61 years of his life. He translated his prize-winning essay into English and it was published in 1786. The essay attracted a lot of attention and enabled him to meet other abolitionists, including Granville Sharp.
In 1787, Clarkson and Sharp were instrumental in forming the Committee for the Abolition of the African Slave Trade. Many of the other members were Quakers. The Committee helped to persuade the member of parliament William Wilberforce to take up the abolitionist cause. Clarkson's task was to collect information for the committee to present to parliament and the public. He devoted his time and energy to travelling around Britain, particularly to the ports of Liverpool and Bristol, gathering evidence about the slave trade from eyewitnesses, especially from sailors who had worked on slave trading ships.
Clarkson also bought examples of equipment used on slave ships, including handcuffs, shackles and branding irons, which he used as visual aids. In 1789, he travelled to Paris where he attempted unsuccessfully to persuade the new French government to abolish the slave trade. Between 1791 and 1792, Clarkson's brother John was involved in the attempt to establish a settlement of former slaves in Sierra Leone in west Africa.
After years of hard work by the Clarksons, Sharp, Wilberforce and many others, the slave trade was abolished in the British empire in 1807. The following year, Clarkson published his book 'History of the Abolition of the African Slave Trade' and, although his health was now failing, continued to campaign for the complete abolition of slavery. In 1833, parliament passed the Slavery Abolition Act, which gave all slaves in the British empire their freedom.
Clarkson retired to Ipswich where he died on 26 September 1846.